 subscribe and order on netflix.com okay guys are you there guys you there can we start now till seven till seven we'll have an hour now because of parkard we got disconnected so uh so we have discussed carbon family they have discussed like i said the you know um glass animal is behavior of carbon elotropes of carbon you'll go through and there is one more thing it is given in ncrt also i realize this now silicates okay you recall this now silicate and then structure of silicates it is given in ncrt like for example ortho silicates ortho silicates pyro silicates pyro silicates cyclic structure or cyclic silicates cyclic silicates all these things are given basically the structure silicates structure it is given in ncrt you just go through okay in this only when you when you see the structure there there is one more thing that we call it as uh infinite chain silicates and then two-dimensional sheet silicates silicates so two-dimensional dimensional sheet silicates so in this there are two types which general form is si2 o5 and minus similarly we have the next one which is three-dimensional sheet silicates okay three-dimensional sheet silicates this actually are of two types of three-dimensional which is feldspar and the second one is zeolite feldspar and zeolites now what do you have to memorize here in feldspar there are you know ortho clays feldspar few examples are given like silzium okay ernotide okay like that so however this feldspar example is not that much important but zeolites also a few properties which is given in ncrt and then few examples of it like we have gemelinite eryedionite these are the few examples of zeolite we have so what are zeolites zeolites are basically uh these are the silicates of you know calcium magnesium sodium all these the complex structure of calcium magnesium sodium and all that's we call it as zeolites so there's a general formula of zeolites definition is also there which is given in the book that is ncrt right so these zeolites basically it acts as an ion exchanger okay however these things are not important okay just you when you go through once you will understand okay these things they don't ask generally but a structure of silicates you must go through which is given in ncrt right so these three four things you have to read from ncrt that's what i have said glass silicates carbon helotropes of carbon that is it okay which is we are left with in this particular um you know uh chapter few compounds like carbon monoxide carbon dioxide is also given in ncrt that already you know it's not required okay so now can we discuss a little bit about boron family so we are starting with group 13 and that is boron family so again boron family we will it's it's a small chapter okay but i don't think we will be able to finish it today but we can finish uh by no next class we'll finish on saturday and then we'll discuss some you know revision on saturday also it will take i think uh one or one and a half hour so like that not more than one and a half or i won't like you know take this so longer one and a half hour maximum okay so whatever we can do we'll do it today and then we'll finish things in the next class and then we'll start some uh equilibrium and all if you want me to discuss some for you know example of your revision right you see first of all the atoms present in group 13 are boron gallium indium and then thallium atomic number you see for boron it is five then we'll add eight so it is 13 18 so 31 49 and then 81 8 18 18 32 other uh what we say magic number electronic configuration 1 s 2 2 s 2 2 p 1 or we can also write helium 2 s 2 2 p 1 for this it will be neon 3 s 2 3 p 1 and here we argon 3d 10 4 s 2 4 p 1 xenon sorry krypton it is a 3d 10 sorry 4d 10 5 s 2 5 p 1 and this will be 4f 14 6d 10 sorry 4f 14 5d 10 6 s 2 6p 1 this is the electronic configuration so the general electronic configuration here it will be what it is ns 2 and p 1 okay so quickly i'll go with the trends that we have okay first of all atomic radius if you see atomic radius i'll give you the value here it does not follow a regular trend here so i'll give you a value to make you understand boron aluminium gallium indium and thallium these values is in picometer 85 143 increases and then decreases then again increases and then almost same increases a little bit okay so now as we go down the group what happens generally atomic size increases but here what happens uh from boron aluminium atomic size is increasing right then what happens from aluminium atomic size is decreasing gallium right then again from gallium atomic size increases atomic size increases gallium to indium and then indium to thallium okay the reason behind this is what that we are adding we are adding a extra shell into this energy shell right extra energy shell into this and at the same time we have weak straining effect of d orbital also yeah so general trend if you see which is given in the book there are many different different factors involved here right so what we can say the radius of these elements does not follow a regular pattern okay it increases from boron to aluminium and then decreases and then increases right it increases from boron to aluminium right decreases from aluminium to gallium and then increases right so we don't have a regular pattern here you see here the another thing you have to take care of that here the difference is too much too much means when you compare the difference here and when you compare the difference here right so here you see the difference is almost a little bit lesser than the twice of this value and when you have difference like this eight or three so since it is in picometer so this difference is very small actually right so that's why in in this group size has a role but the regular trend we don't get over here because of these atomic radius we we have difference here but since the value given is in picometer right picometer this value is given so whatever the difference we have that difference is not that large it is very small difference we have right on the basis of this only if you see the order of first ionization energy of these elements okay so I'll write down in short now boron will have maximum an aluminium and gallium has almost equal value of first ionization energy then gallium is more than to that of indium which is more than to that of gallium so that is what you have to you know keep in mind here that it does not follow a regular trend okay we don't have only size factor here there are other more factors which are involved so this data you have got or I have given you with the value of ionization energy the factual thing right so this is the order follows for ionization energy now on the basis of this if you try to write down the electropositive character right tendency to lose electron okay so it is increases from boron to aluminium as size increases then decreases from aluminium to thallium this is the electropositive character here yeah it will it will affect okay but then again in in organic chemistry the the order or the trend that is given it is based on the fact which is dominating all other factors okay so it's not like in one case we are having only one kind of effect okay we can have two three factors given right so that's why and in the book the order is given it is based on the factors which is dominating over there okay in an organic chemistry actually we have fact first and then we try to explain those facts with the best possible way and what we say that this factor is dominating over there so that's why you have to memorize this thing that where you have to think what what factor is dominating when that's what you have to keep in mind size obviously will affect the properties other properties also but then we have to see suppose we are looking at the stability of carbonates then we have to see what what all other factors are involved there like the pheasant rule thermal like the bond dissociation energy and all so size does have an effect right but what other effects are that also we have to consider and depending on that will give the order but here is that's why here what happens like I said that this factor because of this factor the order is this it does not mean that only that factor is there it means that that particular factor is dominating that's why we are discussing about that factor is it's just that thing okay so electropositive character is this when you see the general electronic configuration is ns2 np1 so its possible oxidation state is what it can have plus one or plus three when it loses one electron from here it is plus one when it loses all these three electron it is plus three so generally here also what happens write down the next thing the tendency to form plus three oxidation state decreases down the group that tendency to form plus three oxidation state decreases down the group and and that of plus one oxidation state increases down the group increases down the group okay reason is same that inert pair effect also we can explain with not fair effect here right next write down reactivity towards reactivity towards air so write down the next thing here which is reactivity towards elements of group 13 forms sorry elements of group 13 reacts with air and forms and forms oxides of oxides of o3 type m2 o3 type write down next line gallium and indium are not affected by air not affected by air next line thallium forms thallium forms an oxide layer on its surface and that is why and that is why it is preserved under oil and that is why it is preserved under oil aluminium also forms of oxide on its surface of oxides on its surface okay you see the reaction boron reacts with o2 around 700 degrees Celsius it forms b2o3 so other oxides if i write down it is b2o3 then al2o3 then we have gallium ga2o3 in2o3 and tl2o3 type of oxide now this oxide it is acidic acidic nature decreases actually down the group these two are amphoteric and these two are basic in nature the reason behind this compound to be acidic is write down here due to its small size has high positive charge density it has high positive charge density and hence it pulls electron pair from h2o it pulls electron pair from h2o and facilitate and facilitate the removal of h plus the removal of h plus that's why it is acidic in nature as you go down the group size increases so positive charge density decreases right so that is not possible over there okay right on in this only next line these elements also forms oxides of ox sorry hydroxides of moh whole three type whole three type these elements also forms hydroxides of moh whole three type the acidity of these hydrides the acidity of these these hydrides also decreases as we go down the group also decreases as we go down the group okay so the first one is acidic again this is acidic these two amphoteric sorry oh i mistake i've written here this acidic these two amphoteric and the last two are basic again in this one you see boh whole thrice is again you see it is electron deficient the structure of doh whole thrice is like this electron deficient and the h2o molecule you have in which oxygen has lone pair of electron and this boron here has one vacant p orbital right so this lone pair of electron it donates to this vacant p orbital of boron and the molecule we get here like this we have ho oh h group this boron has negative this oxygen has positive sign but finally from this what happens h plus comes out any one of these h plus losers one pair of electron here and we'll get what boh minus plus h plus and that is how this acid this boh whole thrice is acidic in nature removal of h plus takes place there okay next you write down the next trend which is nothing but electronegativity write down as we go down the group the electronegativity first decreases from boron to aluminum electronegativity first decreases from boron to aluminum and then increases marginally aluminum to thallium this is again irregular trend we have so again it is important explanation you see here it is because of again irregularities in atomic size so write down the reason behind this due to irregularity in atomic size due to irregularities in atomic size the force of attraction between the nucleus and electrons the force of attraction between the nucleus and electrons decreases as size increases and hence electronegativity decreases the force of attraction between nucleus and electron decreases as size increases and hence electronegativity decreases so this is the reason for boron to aluminum okay now next you write down as the size next line as a size increases the effective nuclear charge also increases right as the size increases effective nuclear charge also increases due to presence of due to presence of fully filled dnf orbital dnf orbital present in between the valence shell electrons and the noble gas core present between the valence shell electron and noble gas core the force of attraction between nucleus and the valence electron increases the force of attraction between nucleus and the valence electron increases and hence electronegativity increases. Electronegativity increases from aluminium to thalium. Next write down electropositive or metallic character. Last one for today. Electropositive, see the reason that I have given you, it is the same thing that we have discussed so far. That is why I am not explaining it. When you read it out, you will understand. Electropositive character or we also call it as metallic character. As we go down the group, as we go down the group, electropositive character increases from boron to aluminium, increases from boron to aluminium and then decreases from aluminium to thalium, increases and then decreases. Reason is also same, the reason that I have given you just now. Write down the explanation in this. Due to increase in atomic size, the ionization in thalpy from boron to aluminium decreases and hence electropositive character increases. So what we can say, size increases, ionization energy decreases, electropositive character increases. So with this what we can conclude that aluminium is a good metal or better metal you can say is electricity, conduct electricity. Since you see boron the ionization in thalpy or if I write down the first three ionization in thalpy, ionization in thalpy of boron is high, is high and hence it is a non-metal. Hence boron is non-metal bad conductor of electricity. Aluminium is a metal, boron is a non-metal. Now again you see it decreases from aluminium to thalium. So write down next line, the next point, the last point here, the gallium, indium and thalium, gallium, indium and thalium, sorry it is thalium, are less likely to lose electrons due to poor shielding effect, are less likely to lose electron due to poor shielding effect and hence less electropositive due to poor shielding effect of DNF orbital and hence let less electropositive. So the best metal in this group is what, aluminium, that is what you have to memorize. Boron is a non-metal, aluminium is a metal and all other elements are has very less tendency to lose electrons because of poor shielding effect of DNF orbital. So this is it, we have discussed few trends, few are left that we will discuss in next class and then we will move on to the written part. Fine understood, can we wind up the class here? When can we have class in the Saturday? If the school is not there, I think morning will be better. Okay, so will you prefer online or offline? Friday morning will be fine, Friday morning, Friday morning online will be fine. Okay fine, okay so let me check with my schedule, most probably we will have class in Friday morning online it will be. Okay, but I will let you know tomorrow. Okay, thank you all, thanks for joining. Do read NCRT, okay? Okay bye, take care.